Uniting the Observed Dynamical Dark Energy Preference with the Discrepancies in $\Omega_m$ and $H_0$ Across Cosmological Probes

TL;DR

This study investigates how assuming a cosmological constant when analyzing data that favors dynamical dark energy can bias measurements of key parameters like $\

Contribution

It demonstrates that biases in $\

Findings

Biases in $\

Discrepancies in $\

Implications for cosmological tensions

Abstract

Recent results from Type Ia Supernovae (SNe), baryon acoustic oscillations (BAO), and the cosmic microwave background (CMB) indicate 1) potentially discrepant measurements of the matter density $\Omega_m$ and Hubble constant $ H_0 $ in $\Lambda$CDM model when analyzed individually, and 2) hints of dynamical dark energy in a $w_0w_a$CDM model when data are combined in a joint analysis. We examine whether underlying dynamical dark energy cosmologies favored by data would result in biases in $\Omega_m$ and $ H_0 $ for each probe when analyzed individually under $\Lambda$CDM. We generate mock datasets in $w_0w_a$CDM cosmologies, fit the individual probes under the $\Lambda$CDM model, and find expected biases in $\Omega_m$ are $\sim 0.03$. Notably, the $\Omega_m$ differences between probes are consistent with values observed in real datasets. We also observe that mock DESI-BAO datasets generated in the $w_0w_a$CDM cosmologies will lead to a biased measurement of $H_0$ higher by ($\sim1.2$km/s/Mpc) when fitted under $\Lambda$CDM, appearing to mildly improve the Hubble tension, but as the true underlying $H_0$ is lower, the tension is in fact worsened. We find that the $\Omega_m$ discrepancies, the high BAO $ H_0 $ relative to CMB, and the joint dynamical dark energy signal are all related effects that could be explained \textit{simultaneously} with either new physics or new systematics. While it is possible to unite many of the discrepancies seen in recent analyses along a single axis, our results underscore the importance of understanding systematic differences in datasets, as they have unique impacts in different cosmological parameter spaces.